Film for photocollographic printing plates



Aug. 31 1926. 1,598,061

M. DE SFERA-rl FILM FOR FHOTOCOLLOGRAPHIG PRINTING PLATES` I original Filed June'4, 1923 '37 wzfffw Patented Aug. 31,

U'NHTED STATES PATENT OFFICE.

MARIANO DI SPEEATI, OF TURIN, ITALY, .ASSIGNOR T0 ARGENTOGRAPHICA (U. S. A.) n

LIMITED, 0F LONDON, ENGLAND.

FILM FOR PHOTGCOLLOGRARHIC PRINTING IIIIQAIIEIS.`

Original application led June 4, 1923, Serial No; 643,435,

application This invention relates to the preparation of photocollographic printing complementary pressure-equalizing portions on their backs of the plates having relief kind described m my copending application Ser. No.643,- 435, filed June et, 1923, now Patent No.

1,587,220, granted June 1,1926, of which the present case is a division, and has for its objectthe provision of in said preparation.

According to the a film adapted for use present invention the film comprises a transparent or translucent support, say of celluloid,

layers, each on one of 'one of said layers which.

the support onv which of and two gelatine support faces, the is on the side of the printing surface the the final printing plate is to be obtained being of such a-character as to be less easily dissolved than the tended to provide relief.

Said two layers them is of a gelatin at a temperature of other layer which is ine pressure equalizing are of gelatin and one of adapted to dissolve say 0 C. while the other one is of a gelatin adapted to dissolve at a somewhat lower temperature, say at40O C.

l The single figure of 1s a transverse section on an enlarged' scale` of a film according to In said figure,

the annexed drawing the' present invention.

1 is a transparent or trans-l lucent support, say of Celluloid, and 2 and 3 are the two gelatin layers above referred to, the layer 2 being of a gelatin adapted to dissolve at a higher temperature thanthe gelatin of layer 3.

For use, said two layer film issensitized by means of' an alkali dried, and then is ex negative image', with 1 fter exposure to both layers is left in bichromate bath and posed 'to light under a ts less-easily dissolved ayer in contact with the negative.

light the gelatin of water-absorbing conand in Italy May 12, 1923. Divided and this dition invregister4 with the dark portions of the negative-while it is made insoluble in both layers in register with thetransparent portions of the negative.

Said ilm is then treated with water at a temperature of 40 C., say vby dipping it in a bath of water having such/a temperature. Such treatment does not affect the layer of gelatin dissolving at '(1. and it merely removes from said layerthe alkali bichromate not acted on by light, while in the other gelatin layer it removesgelatin to a more or less full extent in places where it has not been made insoluble by the action of light on alkali rbichromate-that is, 1n register with dark portionsv of the while gelatin is left unadected in places where it has been acted on by light and made hard-that is, in register with transparent portions of said negative.

By the described treatment the film has on its back side relief portions in register with the hard and ink-retaining portions of its printing layer, while it shows on said back side depressions in register with swelled out portions of said printing layer.

Reference is made to my previously mentioned copending application Ser. No. 643,- 435, in respect of features not claimed in-the present application.

What I'claim as my invention and desire to Secure by United States Letters Patent isz- A film for use in making photocollographic printing plates having a layer of gelatin on each face ers being made of gelatin which is adapted to dissolve at a lower temperature than the'l gelatin providing the other one of said layers.v

In-testimomhereof I affix SPERATI.'

negative,

thereof, one of said lay- 

